Surgical procedures for the repair or fusion of small bones, ligaments and tendons, require use of a prosthetic or orthotic device or suture which can bear a heavy load caused by the unique anatomical features of the compromised bone or tendon. For example, fractures of the patella are exposed to high stresses during flexion and extension of the knee joint; fusions of the spinal vertebrae are exposed to high gravitational forces and movements of the spinal column; and torn ligaments and tendons are exposed to high stresses due to contraction of the associated muscles or flexion and extension of the bony structures.
An orthotic, prosthetic device or suture used in such fashion must be able to bear heavy stress loads, be flexible enough to achieve the desired repair, and be sufficiently inelastic to maintain alignment of the anatomical structures for proper fusion and repair.
Materials currently available for such surgical procedures include synthetic or wire sutures, metal cable and various specialized prosthetic or orthotic devices. Synthetic and metal sutures are susceptible to fatigue and breakage during application and use. The currently available synthetic suture materials have insufficient strength and stiffness to provide the stress sharing and strain-limiting capabilities required. Metal cable or wire sutures, while providing additional strength, lack the flexibility required for many fusion and/or repair procedures.
Satisfactory repair or fusion requires that the bones or bone fragments remain sufficiently immobilized to permit healing. Current procedures for the repair or fusion of small bones including vertebrae and the patella, restrict motion of the bones or bone fragments by wiring the elements into the appropriate position. The applied surgical wire is generally bent tightly around the bone fragments and two ends of the wire are generally twisted together to provide compressive force.
Breakage of wire sutures or cables may occur with bending during implantation of the device or post-implantation movement generating repetitive bending stresses. Failure of the wire to supply sufficient compressive force and apposition of bone fragments results in reduced or failed healing of the bones. Sharp wire points caused by wire breakage in situ can result in significant damage to surrounding tissues and/or joint capsules.
Metal suture material is radiopaque, and interferes with efficient X-ray monitoring of bone fusion and repair. Metal sutures also interfere with the use of magnetic resonance imaging diagnostic procedures which require that no metal be present in the vicinity of use.
It would be highly desirable to provide a small diameter, flexible, load bearing suture to replace low strength polymeric or synthetic sutures and metal sutures for use in the fusion, repair, and augmentation of small bones, ligaments, and tendons.